1. Field of the Invention
The present invention relates to an induction system for a watercraft having an outboard motor.
2. Description of the Related Art
Known outboard motors mix ambient air entering through the engine's cowling with fuel. The air/fuel mixture is burned in one or more cylinders of the motor to generate power and propel the watercraft. The output efficiency of the engine may decline if the air/fuel mixture contains excessive moisture.
Since watercrafts operate in a wet environment, the opportunity exists for water or moisture to be added to the air entering the engine. Accordingly, it is desirable to reduce the chance that water or moisture is in the intake air. If the air includes moisture, it is desirable to remove the moisture from the air before the air is mixed with the fuel.
Patent Document JP-A-2004-239156 discloses a structure which separates moisture from air containing moisture. The specification states, “Air flowing into each side air duct through an ambient air intake formed at the duct passes through an air passage which is bent, on the way to its goal; thereby, the air is compulsively turned sideward. Moisture thus is separated from the air containing the moisture. Further, the air flowing into a downstream intake chamber via a communicating port is compulsively turned to a vertical direction so that again remaining moisture is further separated. The air from which the moisture is separated in the two stages is mixed with fuel.” The air flows from lateral sides of the watercraft because the ambient air intakes are located at the respective side air ducts. However, moisture from side waves during turning and from other waves during normal running conditions may still enter the air intakes. The structure further does not prevent raindrops from entering the air intakes. In addition, the downstream intake chamber into which the air flows has a vertically extending chimney-shaped structure. It is difficult to sufficiently block moisture when there is a large amount of moisture or a large water splash.
U.S. Pat. No. 5,078,629 discloses a structure which inhibits moisture from mixing with air. The specification states, “A transom board of the hull has an opening and a cowling of an outboard motor has an air port for taking air for combustion. The opening and the air port are connected to each other through a duct; thereby, air is taken from a location in the hull.” “The air hardly contains moisture in comparison with the case in which the cowling of the outboard motor has an intake opening and air is taken through the intake opening.” With this structure, air enters through an opening in the transom board. However, if rain falls into the hull or waves enter the hull, moisture may enter the openings in the transom and mix with the air. Further, the structure routes the intake air through the cowling but does not provide a passage to the engine. Thus, the intake air may be warmed before it reaches the motor.
In the air intake structures above, moisture from waves may still mix with the air or the air may be warmed as the air is routed between the transom and the engine.